> For the complete documentation index, see [llms.txt](https://excelhelp.windhamlabs.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://excelhelp.windhamlabs.com/functions/exposure-to-loss/losspr.md).

# LOSSPR

## Description

Probability of loss is a measure of the likelihood that a portfolio will incur a particular percentage of loss at the end of an investment horizon. The function is also able to calculate the within-horizon probability of loss which is estimated as a first-passage time probability.

{% hint style="info" %}
See <https://insights.windhamlabs.com/insights/rethinking-exposure-to-loss> for an introduction to stress testing your portfolios and assessing a more realistic measurement of exposure to loss.
{% endhint %}

## Syntax

The following describes the function signature for use in Microsoft Excel's formula bar.

```excel-formula
=LOSSPR(mu, sigma, horizon, lossThreshold, estWithinHorizon)
```

### Input(s)

| Argument             | Description                                                                                                                                                                          |
| -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **mu**               | Required. Vector / scalar of portfolio return estimate(s).                                                                                                                           |
| **sigma**            | Required. Vector / scalar of portoflio risk estimate(s).                                                                                                                             |
| **horizon**          | Required. Investment time horizon in the same time units of mu and sigma.                                                                                                            |
| **threshold**        | Required. Loss threshold to assess likelihoods.                                                                                                                                      |
| **estWithinHorizon** | Optional. Logical flag (TRUE or FALSE) to indicate whether you would like to calculate the within-horizon risk measurement. If this argument is not specified, it defaults to false. |

### Output(s)

Probability of loss estimate(s).

## Example

![](/files/-MLDbLMsWQNpZ1zY5cCR)

{% file src="/files/-MLDbQpbZVBrMJlEQfnG" %}
Example Workbook: LOSSPR
{% endfile %}